There are a variety of applications in which it is desired to form an opening through a sheet of metal, rapidly and without requiring excessively large pressures. It is often desirable to do this in conjunction with the insertion of a threaded drill screw into the opening so formed in the work-piece.
For example, in the building construction industry it is often desirable to secure material, such as thermal insulation, to the sheet metal which forms the walls or roofs of metal buildings. To do so, it is common to employ a so-called drill screw which, when rotationally driven by a drill tool, pierces the insulation and sheet metal and then screws itself into and partially through the hole formed in the sheet metal, until a large washer-like plate under the head of the drill screw is pulled tightly against the exterior of the insulation to secure it in place.
The sheet metal used for this purpose is usually of #18 to #26 gauge steel, corresponding to sheet thicknesses of from about 0.050 to 0.030 inch. While steel sheet having a thickness near the lower end of this range (e.g. #22 gauge) can usually be drilled and the drill screw inserted and seated quite easily and quickly, the time and force necessary to insert a drill screw properly in thicker steel, e.g. #18 gauge steel, are often much greater than is desirable, and with some drill screws this cannot be accomplished at all.
One type of drill screw which has been employed for such purposes is similar to that shown in U.S. Pat. No. 3,221,588 of G. L. Wieber issued Dec. 7, 1965. While such a drill screw will generally pierce the steel sheet and seat itself in #22 gauge steel in about 3 to 4 seconds with an applied force of about 30 pounds, in the case of #18 gauge steel it may more typically require about 6 to 8 seconds, and in some cases it may not succeed in piercing the metal at all.
Accordingly, it is an object of the present invention to provide a new and useful drill tip and a fastener employing same.
Another object is to provide a drill tip and drill screw employing same which operate quickly and well, even in relatively thick steel sheets.